If the roots of the equation x^2 + 6x + k = 0 are -2 and -4, what is the value o

Practice Questions

Q1
If the roots of the equation x^2 + 6x + k = 0 are -2 and -4, what is the value of k?
  1. 4
  2. 8
  3. 10
  4. 12

Questions & Step-by-Step Solutions

If the roots of the equation x^2 + 6x + k = 0 are -2 and -4, what is the value of k?
  • Step 1: Identify the given quadratic equation, which is x^2 + 6x + k = 0.
  • Step 2: Note the roots of the equation, which are -2 and -4.
  • Step 3: Use the formula for the sum of the roots. The sum of the roots is -2 + -4.
  • Step 4: Calculate the sum: -2 + -4 = -6.
  • Step 5: According to the quadratic formula, the sum of the roots (which is -6) should equal -b/a. Here, b = 6 and a = 1, so -b/a = -6.
  • Step 6: Now, use the formula for the product of the roots. The product of the roots is -2 * -4.
  • Step 7: Calculate the product: -2 * -4 = 8.
  • Step 8: According to the quadratic formula, the product of the roots (which is 8) should equal k.
  • Step 9: Therefore, we find that k = 8.
  • Quadratic Equations – Understanding the relationship between the coefficients of a quadratic equation and its roots through Vieta's formulas.
  • Sum and Product of Roots – Using the sum and product of the roots to find unknown coefficients in a quadratic equation.
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